This year, partly in collaboration with other laboratories, our group published eight scientific articles related to DNA replication fidelity. We showed that incorporation of ribonucleotides during eukaryotic nuclear DNA replication results in large forms of chromosomal instability in budding yeast, loss-of-heterozygosity and nonallelic homologous recombination. Both forms of instability are largely, if not exclusively, due to topoisomerase 1 incision of ribonucleotides incorporated by DNA polymerase epsilon, the primarily leading strand replicase. We showed that DNA polymerase elta, which primarily replicates the lagging strand of DNA during normal DNA replication, replicates both DNA strands after homologous recombination-dependent fork restart at a well-defined replication fork barrier in fission yeast. We showed that a dNTP pool imbalance in budding yeast that is driven by a mutation in ribonucleotide reductase reduces the fidelity of DNA replication in a manner consistent with the pool imbalance. We published three articles that reviewed recent work on replication fidelity and its implications for evolution and the origins of human diseases. We published an article highlighting our method to monitor ribonucleotide incorporation across the whole budding yeast genome, and awe published an article discussing our preferred model of eukaryotic nuclear DNA replication enzymology in relation to an alternative viewpoint published by another laboratory.